[runtime] Add instance size check for CheckEquivalent().

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 2689f3f6cb9bf5c80c88d49bd2ff5307ae83c44d..e919c44f4e1dfd392fc3ff745ee3dba57048869c 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -12296,7 +12296,9 @@ bool Map::EquivalentToForNormalization(Map* other,
   int properties =
       mode == CLEAR_INOBJECT_PROPERTIES ? 0 : other->GetInObjectProperties();
   return CheckEquivalent(this, other) && bit_field2() == other->bit_field2() &&
-         GetInObjectProperties() == properties;
+         GetInObjectProperties() == properties &&
+         JSObject::GetInternalFieldCount(this) ==
+             JSObject::GetInternalFieldCount(other);
 }